The present invention is directed to control of power conversion devices such as AC-DC voltage converters, and especially to power factor correction converters. Many electronic equipments use a switching power supply device to power internal circuits. Switching power supply devices include power converting circuitry such as voltage converter circuitry. A switching power supply device may be either an AC (alternating current) or a DC (direct current) power supply unit. Either type of power supply unit, AC or DC, itself imposes a non-linear load on a line to which it may be attached. A non-linear load may result in low power factor, low efficiency, harmful electromagnetic interference (EMI) with other electronic equipment or other undesirable effects.
The problems caused by non-linear loads are addressed by harmonic standards proposed for electronic equipment by international agencies. In order to meet such standards, product designers require switching power supplies with appropriate power factor correction converter circuitry. Such power factor correcting (PFC) converters are controlled to reduce harmonics in current drawn by the power supply produce in which they are employed, correct phase of current drawn and make the power supply look like a pure resistor as viewed from AC supply terminals into the power supply.
PFC signal converters are available, but those with higher precision performance require complex control circuitry. Such increased complexity increases costs for producing such PFC signal converters. There are simpler, lower cost solutions that are used in low power, low efficiency applications; i.e., low performance signal converters.
There is a need for a simplified power factor correction (PFC) control apparatus that can be cost-effectively implemented for use with low cost, low power applications without sacrificing performance.